In a second assault, a roadside bomb exploded near a security checkpoint in southern Arish, killing one army officer and wounding three others, security sources said.
The violence came days ahead of an investment conference in the resort of Sharm el-Sheikh, 340 km (210 miles) south of al-Arish, that Egypt hopes will project an image of stability and attract billions of dollars.
The attacks were concentrated in North Sinai, epicentre of an insurgency by militants seeking to topple the Cairo government.